Well, it can be a sign but it often isn't as well. Questions that are important about this are when was the first day of her last period and when did you have unprotected intercourse? That will give us a better idea. But things that can make you late besides pregnancy are stress, anxiety, changes in routine, illness, weight gain or loss. She can take a pregnancy test 2.5 weeks after the episode she is afraid about for an accurate test result.